ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-11-3359-2011Space-based evaluation of interactions between aerosols and low-level Arctic clouds during the Spring and Summer of 2008TietzeK.14RiediJ.2StohlA.3GarrettT. J.11Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT, USA2Laboratoire d'Optique Atmosphérique, Université de Lille1/CNRS, France3Norwegian Institute for Air Research, Kjeller, Norway4deceased0804201111733593373This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/11/3359/2011/acp-11-3359-2011.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/3359/2011/acp-11-3359-2011.pdf

This study explores the indirect effects of anthropogenic and biomass
burning aerosols on Arctic clouds by co-locating a combination of
MODIS and POLDER cloud products with output from the FLEXPART tracer
transport model. During the activities of the International Polar
Year for the Spring and Summer of 2008, we find a high sensitivity
of Arctic cloud radiative properties to both anthropogenic and biomass
burning pollution plumes, particularly at air temperatures near freezing or
potential temperatures near 286 K. However, the sensitivity is much lower at both
colder and warmer temperatures, possibly due to increases
in the wet and dry scavenging of cloud condensation
nuclei: the pollution plumes remain but the component that influences
Arctic clouds has been removed along transport pathways. The analysis shows that,
independent of local temperature, cloud optical depth is approximately four times
more sensitive to changes in pollution levels than is cloud effective radius. This
suggests that some form of feedback mechanism amplifies the radiative
response of Arctic clouds to pollution through changes in cloud liquid water path.